Uncontrolled cell growth is a distinguishing feature of tumors and other cancers. Surgical intervention seeks to remove the tumor mass. Various other techniques, such as chemotherapy and radiation, target and kill cancer cells, including those left behind after surgery and those located away from the primary tumor mass. Newer techniques employ the body's own defenses including immunological reactions against the aberrant cells.
In concert with uncontrolled cancer growth, cells often exhibit a failure of programmed cell death, or apoptosis. Healthy cells follow a built-in cycle of cell division, growth, and apoptosis. However, transformation to a cancerous or neoplastic state may give rise to genetic modifications that protect the abnormal cell against the action of molecules that typically trigger apoptosis. Cells normally programmed to die survive and continue to divide, thus propagating the cancer.